Lighting on helmets is not new. U.S. Pat. No. 4,195,328 shows an early lighting system providing for an auxiliary headlight to be mounted on a safety helmet 26. The light utilizes a halogen quartz lamp 124 with a reflector 126. In order to address heating concerns, slots 114,118 with a perforated lens cover 116 so as to “permit a dissipation of any internal heat from lighting elements.” Such a heat removal system would probably work for halogen lighting but would not be expected to satisfactory remove heat from a high power LED. Other lighted helmet constructions include U.S. Patent Application Nos. 2008/0080171, 2008/0170382, 2008/026638 and 2005/0265015.
U.S. Pat. No. 5,871,271 discusses the use of a ten candle power LED as a headlight which would appear to be a low power LED. A common conversion in the green light spectrum is believed to be 680 lumens per watt. 12.7 lumens are a candle power. A conversion of ten candle power to watts provides what appears to be a LED having a maximum output wattage of approximately 0.2 watts. High power LEDs are commonly provided today are at least one, if not five or ten watts. A principal difference between high and low power LED is that a low power LED may provide sufficient lighting so that a rider might have increased visibility for safety concerns, while a high power LED would be much better suited for use as a headlight to illuminate a source at a distance. The headlight of the '271 patent is not expected to provide significant illumination at a distance.
Even though U.S. Pat. No. 5,871,271 discloses the use of a ten candle power LED: “the headlight or reading function can be enhanced by using high brightness LEDs such as the 10 candlepower white LEDs manufactured by Toshiba Corporation, “high power LEDs are not a viable commercial option at this time. Furthermore, based on the construction of placing the LEDs in a recess of the hard shell outer layer and not providing any separate heat removal capability as is shown in FIGS. 2, 3a and 3b, a high power LED substituted for a low power LED in that construction would result in burn out almost instantaneously due to the heat buildup and absence of a heat sink (low power LEDs do not normally require a heat sink of any significant size). The '271 patent is believed to show the use of lights on bicycle helmets principally for the use of identifying the rider as opposed to illumination as a headlight.
References such as U.S. Pat. No. 6,955,444 show a surgical head light in which high powered LEDs are employed such as a one watt and a five watt LED which explicitly describe the need for a heat sink. There is no room for this bulky heat sink in constructions such as the '271 patent. The '444 patent describes a five watt LED requiring a heat sink four times that use for a one watt LED. The applicant and the owner of the '444 patent have found that when purchasing an LED strong enough to provide headlights which can be clamped on to the head of the user such as on the helmet, that the heat sinks are heavy and bulky and thus “contribute[s] to discomfort for the wearer of the head mounted lamp” (Column 1, lines 45-48). In order to overcome the discomfort of heat sinks for high powered LEDs at five watts, this owner of the '444 patent used three watt LEDs so that smaller heat sinks could be employed with such constructions than would otherwise be required for higher wattage bulbs.
Of course, references are available directed to various LED heat sinks such as U.S. Pat. No. 6,799,864, U.S. Pat. No. 7,040,388, U.S. Pat. Nos. 5,173,839, 7,489,031, 6,827,130 and 6,999,318 and probably others. Similarly, there are patents related to the cooling of helmets such as U.S. Pat. Nos. 6,598,236, 7,219,371, 7,296,304, 7,010,813 and others.
Nevertheless, in spite of the prior art related to the general idea of providing a helmet with LEDs or providing a head lamp for the head of a user, the applicant believes that a lightweight helmet without a separate bulky high power LED heat sink is needed for at least some applications with improvements over the prior art are believed to be necessary in various applications.
Heat pipe technology has long been used in various devices for the efficient removal of heat away from heat sources which are particularly susceptible to the heat generated by their operation. Heat pipe technology utilizes the concept of latent heat of vaporization of a working fluid contained in a closed container such as a pipe form. In the phase change from liquid to vapor phase a large amount of heat can be absorbed and transfer from a “hot side” to a “cold side” of the container. The container itself is typically a tube and oriented in a way that maximizes this transfer of heat. The working fluid can be any of a number of substances depending on the particular operating temperature range at which the device is to be maintained. Examples of this are U.S. Pat. No. 7,701,708 B2 which utilizes heat pipes to remove heat from a CPU in a computer to a radiator fin assembly. Similarly, U.S. Pat. No. 7,719,839 B2 claims use of a heat pipe for transfer of heat to a radiator “cold plate” with the ability to add different sized radiator assemblies to the heat pipe in order to increase the quantity of heat the system can dissipate. Fujitsu designed and patented a heat pipe assembly, U.S. Pat. No. 7,721,789 B2, which as its goal was to provide a more form of a heat pipe base cooling apparatus for use in a variety of devices. The unique nature of Fujitsu's device is the u-shaped configuration allowing for the required length of pipe for expansion of the working fluid as it changed to the gas phase. They sited the problem addressed by their device as that of size of previous heat pipe cooling devices which require long segments of straight pipe to achieve cooling and thus arrived at their U or V shaped configuration. They then pass their heat pipe through radiator fins to remove the heat from their heat pipe. U.S. Pat. No. 7,723,845 B2, U.S. Pat. No. 7,723,835 B2, U.S. Pat. No. 7,746,640 B2, U.S. Pat. No. 7,740,054 B2 and U.S. Pat. No. 7,742,306 B2 have in common use of heat pipe type conductors as one component of an assembly directed at moving heat away from the heat generating source to a heat radiating structure such as a fin assembly with or without additional air moving fans/ventilation to increase conductive cooling at the radiator.
Over the past few years, use of heat pipes to specifically cool light emitting diodes (LEDs) has been the subject of a variety of patents. Heat pipes, being very compact and efficient conductors of heat lend themselves very naturally to incorporation into lighting devices utilizing LEDs as the light source due to the heat sensitive nature of LEDs and their requirement to be maintained below some maximum operating temperature to avoid damage to the light-generating phosphor element. In U.S. Pat. No. 7,726,844 B2, an LED is mounted to a heat dissipating device which utilizes a hollow chamber filled with a working fluid but does not specifically claim the use of a heat pipe in terms of the unique benefit of liquid to gas (and gas to liquid, i.e. condensation) phase change for transfer of heat. U.S. Pat. No. 7,744,257 B2, U.S. Pat. No. 7,744,250 B2, U.S. Pat. No. 6,831,303 B2, U.S. Published Patent Application No 2008/0150126 A1, and U.S. Pat. No. 7,736,032 B2 are all patents for devices that utilize heat pipes in various configurations to couple LEDs to adjacent heat sink and/or heat radiating fins that have been incorporated into the overall design as the cold side of the heat pipe. These patents deploy heat pipes in the conventional manner as part of their overall design and that is as a heat conduit for the express purpose of movement of heat between the heat source and the heat sink element of their device.
The use of heat pipes as conductors/conduits for the movement of heat is the routine method in which they are incorporated as parts of large devices and machines. U.S. Pat. No. 7,32,918 B2 is a device that takes a new step in the realm of heat pipe technology in that it takes advantage of carbon nanotube technology to further increase the efficiency of heat transfer from the heat source to the working fluid where the liquid to gas phase change can move heat to the top of the chamber and into a hollow pin fin structure. In the hollow pins the vapor can condense and thereby transfer heat to a large surface are to be radiated/conducted to the surrounding atmosphere.